In my co-pending application having the Ser. No. 659,199 and the title FILTER AND DETECTOR AND METHODS OF USING SAME IN THE REMOVAL AND DETECTION OF CARBON MONOXIDE FROM, AND IN, A GAS STREAM, I have described the fact that packed red cells can remove from a gas stream up to about four times the quantity of CO which can be accounted for on the basis of the hemoglobin present. I have attributed the unexpectedly enhanced efficacy of the composition in removal of CO from the gas stream to an enzyme, carbon monoxidase, hereinafter referred to as CMase. As will become apparent, the removal of CO from a gas stream such as tobacco smoke must be due, at least in part, to oxidation of CO to CO.sub.2 by this enzyme. Moreover, the fraction of CO converted to CO.sub.2 is sufficiently great so that the enzyme can be used as the basis for a device for detecting the presence of CO in a gas stream or in the ambient atmosphere.
Once the existence of an enzyme effective for the conversion of carbon monoxide was postulated, a number of previously unexplained results which had been reported in the literature immediately fell into place. One of the earliest publications pertinent to the present invention was that of Esther M. Killick in the Journal of Physiology (1948), 107, 27-44, entitled THE NATURE OF THE ACCLIMATIZATION OCCURRING DURING REPEATED EXPOSURE OF THE HUMAN SUBJECT TO ATMOSPHERES CONTAINING LOW CONCENTRATIONS OF CARBON MONOXIDE. Killick cited the results of experiments going back as far as 1856 to show that men and women whose occupation involved frequent exposure to low concentrations of CO develop a certain degree of tolerance to this gas. Experiments were also carried out by Haldane and Priestly, the results being reported in 1935. These tests also gave the same results, namely, that humans develop a degree of tolerance or acclimatization to CO.
Killick's results showed conclusively that a tolerance to CO can be developed by exposure to this gas, the tolerance being shown by a lower level of COHb in the blood of an acclimatized subject as compared with that of an unacclimatized subject, both being in equilibrium with some concentration of CO in alveolar air. Killick failed to provide a satisfactory explanation for the phenomenon, but her results are conclusive.
A. Kistner, in the Proceedings of the Section of Sciences, Koninklijke Nederlandse Akademie van Wetenschappen, Vol. LVI, Series C, 443-450 (1953), under the title "On a Bacterium Oxidizing Carbon Monoxide," provided a survey of the literature. He gives a reference to H. Kaserer, Centr. Bakt, Parasitenk. II, 16, 681, 769 (1906), who attempted to isolate hydrogen-oxidizing bacteria. He postulated the following reactions: EQU H.sub.2 CO.sub.3 + H.sub.2 = CO + 2H.sub.2 O EQU 2co + o.sub.2 + 2h.sub.2 o = 2h.sub.2 co.sub.3
as is evident, this mechanism includes a step in which Co is oxidized by oxygen. Although the evidence was weak, Kaserer claimed the discovery of carbon monoxide oxidation by microorganisms.
C. Wehmer, in Berichte 59, 887 (1926), brought illuminating gas into contact with garden soil and observed a decrease in carbon monoxide concentration. However, there was no effect when the same test was carried out with sterilized soil. Evidently, an organism or enzyme effective for the conversion of carbon monoxide was present. Kistner actually isolated an organism from garden soil, pure cultures of which could develop in a carbon monoxide-containing atmosphere. Nevertheless, Kistner failed to carry his work forward in the direction of isolating the factor in the bacteria responsible for the conversion of CO.
E. W. Chappelle, in Biochimica Et Biophysica Acta, 62 (1962), 45-62, reported on Carbon Monoxide Oxidation by Algae. Chappelle showed that CO is oxidized to CO.sub.2 in the presence of green algae and oxygen and that the rate is increased several-fold in the presence of light.
As is evident from the above citations, the ability to convert CO, generally to CO.sub.2, is present in mammals, plants and bacteria. This is reasonable from the standpoint of evolution, since CO is ubiquitous, and it is likely that this ability is even more widespread, being present in many species of both plant and animal phyla.
The capacity to cope with CO, as noted in my co-pending application, almost certainly stems from the fact that the atmosphere contains a small but by no means negligible quantity of CO. Significantly, although this capacity for converting CO has been recognized in mammals, bacteria and plants, it has not been recognized that there may be a specific factor or factors responsible for the conversion and that isolation of such a factor or factors may be of value for the removal and detection of CO from ambient atmosphere or from gas streams. Further, while in my co-pending application, I have taught how the factor present in mammalian blood may be utilized, note is taken of the fact that utilization of mammalian blood for the purposes specified may not represent the most economic means of reaching the stated objectives. Consequently, there is value in establishing processes for isolation and utilization of such a factor or factors when derived from bacteria and from plants, as well as from blood, the term "plants" herein being taken to include algae and fungi.